To recover hydrocarbons (e.g., oil, natural gas) it is of course necessary to drill a hole in the subsurface to contact the hydrocarbon-bearing formation. This way, hydrocarbons can flow from the formation, into the wellbore and to the surface. Recovery of hydrocarbons from a subterranean formation is known as “production.” In some productions, a casing is installed in the drilled wellbore to provide a structurally-sound conduit to retrieve hydrocarbons. In other productions, hydrocarbons are retrieved from an uncased or “openhole” well.
In openhole well production, one key parameter that influences production rate is the permeability of the formation along the flowpath that the hydrocarbon must travel to reach the wellbore. Sometimes, the formation rock has a naturally low permeability; other times, the permeability is reduced during, for instance, drilling the well. When a well is drilled, a fluid is circulated into the hole to contact the region of the drill bit, for a number of reasons—including, to cool the drill bit, to carry the rock cuttings away from the point of drilling, and to maintain a hydrostatic pressure on the formation wall to prevent production during drilling.
Drilling fluid is expensive particularly in light of the enormous quantities that must be used during drilling. Additionally, drilling fluid can be lost by leaking off into the formation. To prevent this, the drilling fluid is often intentionally modified so that a small amount leaks off and forms a coating or “filtercake” on the openhole wellbore.
Once drilling is complete, and production of the formation via the openhole wellbore is desired, then this filtercake must be removed in order to achieve the targeted productivity. Current cleanup methodology includes applying chemical treatment to dissolve filtercake and near-wellbore damage and/or applying a jet blasting along the wellbore to mechanically break down the filtercake. In long horizontal well, these processes take a considerable amount of time to complete. As a result, when a local section is first cleaned, it becomes conducive for channeling the treating fluid to flow into, leaving majority of the sections not covered by the treating fluid. This inability to uniformly cleanup the entire well is a major problem facing the oil industry when trying to produce from long openhole wells. The second drawback of the current methodology is the inability to deliver the treating fluid deep into the formation beyond the drilling damage. Thus, maximum cleanup of filtercake is not achieved even in the areas that do receive the treating fluid. Because of the combination of these two problems—uneven coverage and shallow penetration of treating fluid—borehole completions often do not perform up to the expectations.
Accordingly, a need exists in the drilling and completions industry for a reliable system for removing filtercake quickly, efficiently, and completely in order to produce the well. This is the primary objective of the present invention.